java实现网页的验证码的改良版(火狐可点击刷新)

util包
package www.csdn.net.news.util;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.util.Random;

import javax.servlet.http.HttpSession;

public class RandomImage {
	private final static int WIDTH = 100;
	private final static int HEIGHT = 30;
	public static Random rd = new Random();

	public static BufferedImage creatImage(HttpSession session) {

		// 在内存中创建图片
		BufferedImage image = new BufferedImage(WIDTH, HEIGHT,
				BufferedImage.TYPE_INT_BGR);
		// 得到图形上下文
		Graphics g = image.getGraphics();
		// 设置背景
		drawBackground(g);
		// 绘制边框
		drawBorder(g);
		// 绘制内容

		
		// 将验证码信息发送到当前页的session中
		String code=String.valueOf(drawContent(g));
		System.out.println(产生验证码=======+code);
		session.setAttribute(code, code);

		// 绘制干扰
		drawDisturb(g);

		return image;
	}

	private static String drawContent(Graphics g) {
		// TODO Auto-generated method stub
		String con = qwertyuiopasdfgjklzxcvbnm1234567890QWERTYUIOPASDFGHJKLZXCVBNM;
		//用于显示
		StringBuffer sb = new StringBuffer();
		//用于验证
		StringBuffer st=new StringBuffer();
		for (int i = 0; i < 4; i++) {
			int index = rd.nextInt(con.length());
			char str = con.charAt(index);
			sb.append(str+ );
			st.append(str);
		}
		g.setColor(getRandomColor(10, 100));
		g.setFont(new Font(Gungsuh, Font.BOLD, 20));
		g.drawString(sb.toString(), 15, 20);
		System.out.println(st+=====================);
		return st.toString();
	}

	private static void drawDisturb(Graphics g) {
		// TODO Auto-generated method stub
		g.setColor(Color.blue);

		for (int i = 0; i < 2 * (WIDTH + HEIGHT); i++) {
			int x1 = rd.nextInt(WIDTH - 10);
			int y1 = rd.nextInt(HEIGHT - 10);
			/*
			 * int x2 = rd.nextInt(WIDTH); int y2 = rd.nextInt(HEIGHT);
			 */
			// /g.drawLine(x1+5, y1+5, x2-5, y2-5);
			g.setColor(getRandomColor(1, 255));
			g.drawOval(x1 + 5, y1 + 5, 1, 1);

		}

	}

	private static void drawBorder(Graphics g) {
		// TODO Auto-generated method stub
		g.setColor(Color.yellow);

		g.drawRect(0, 0, WIDTH - 2, HEIGHT - 2);
	}

	private static void drawBackground(Graphics g) {
		// TODO Auto-generated method stub
		g.setColor(getRandomColor(100, 255));
		g.fillRect(0, 0, WIDTH, HEIGHT);
	}

	// 生成随机图片颜色
	private static Color getRandomColor(int fc, int bc) {
		Random random = new Random();
		if (fc > 255) {
			fc = 255;
		}
		if (bc > 255) {
			bc = 255;
		}
		int r = fc + random.nextInt(bc - fc);
		int g = fc + random.nextInt(bc - fc);
		int b = fc + random.nextInt(bc - fc);
		return new Color(r, g, b);
	}

}


servlet代码
package www.csdn.net.news.servlet;


import java.io.IOException;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import www.csdn.net.news.util.RandomImage;



public class ImageServlet extends HttpServlet {

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		System.out.println(imgservlet第一次被执行);
		// 通知





浏览器以图片的方式打开  
        response.setContentType(image/jpeg);  
        
        
        // 设置浏览器不要缓存  
        response.setIntHeader(expires, 0);  
        response.setHeader(cache-control, no-cache);  
        response.setHeader(pragma, no-cache);  
    	System.out.println(imgservlet第二次被执行);
    	ImageIO.write(RandomImage.creatImage(request.getSession()), jpeg, response.getOutputStream());
	
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		this.doGet(request, response);
	}

}

jsp代码
<%@ page language=java import=java.util.* pageEncoding=UTF-8%>
<%
	String path = request.getContextPath();
	String basePath = request.getScheme() + ://
			+ request.getServerName() + : + request.getServerPort()
			+ path + /;
%>

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